1. Field of Invention
The present invention relates to a decoding method and apparatus. More particularly, the present invention relates to a decoding method which utilizes temporally ambiguous code and apparatus using the same.
2. Description of Related Art
Today, computer is powerful and small enough to be carried around, in the form of many tiny devices (cellphone, MP3 Player, etc.). The Man Machine Interface (MMI) becomes a challenge due to the limited size of a device. For text input, current solutions include traditional multitap, predictive text input, and small QWERTY keyboards.
The traditional multitap, known as ABC input method, is simple but inefficient and hardly to be mastered. Small QWERTY keyboard assumes that users are familiar with the traditional QWERTY keyboard and this familiarity can be well transferred to the tiny QWERTY keyboard. The first assumption is limited to the PC users but many teenagers may master text input on cellphone before they master the QWERTY keyboard. Although this arrangement may help computer users to find characters more easily than scattered or alphabetic order, the even much smaller key size reduces the usability considerably.
On the other hand, predictive text input greatly reduces the keys required per character over multitap by introducing new problems: (a) predicted text is randomly changed while user input; (b) users can hardly check their typing correctness during input and typo recovery is irritating; (c) upon missed word in its dictionary, users are required to use another input method (typically multitap) and restart again; and (d) the behavior in summary is non-predictable and unreliable in the sense of perception as well as performance.
Furthermore, given a mapping which maps encoding sequences to decoding sequences wherein each encoding sequence is a token, it is so called “spatially ambiguous” if there are multiple mappings for a token. An example of spatially ambiguous is shown in FIGS. 1A and 1B. Refer to FIGS. 1A and 1B, wherein FIG. 1A is a keyboard of a common prior art and FIG. 1B is the spatially ambiguous mapping accordingly. The keypad 100 contains a plurality of keys 101 with a numeral, and special function keys 104 and 105. The traditional spatial ambiguity groups some symbols 103 in a decoding symbol set together and then assigns the said group to a symbol 102 of an encoding symbol set.
After mapping to the domain of encoding symbol set, it is impossible to distinguish the grouped symbols purely base on knowledge of this domain. This process can be viewed as a lousy encoding. To recover the lost information, all possible combinations may be generated and let user choose the correct one.
Multitap resolves spatial ambiguity at character level and lets users roll and choose the intended symbol in the group for each input.
Furthermore, traditional predictive text inputs resolve spatial ambiguity at word level. Take an input of “HOME” for example and illustrated in FIG. 1B. An encoding symbol 110 of the input sequence “4663” represents one decoding symbol 112 of a group 103. A linked network 111 shows all combinations of adjacent encoding symbols. Due to the combinations of an input sequence is M^L, where M is the size of a symbol group and L is the input length, it is infeasible to enumerate all combinations (for this case, the combinations are 3^4=81, but once L=10, it will be 3^10=59049).
Typically, linguistic knowledge can be used to greatly reduce the possible outcomes. A common practice is providing a word dictionary to match up and output those words for user to choose. However, even the linguistic knowledge is introduced, the input sequence “4663” can still be interpreted in many ways such as “HOME”, “GOOD”, “GONE”, “HOOD”, “HOOF”, “HONE”, “GOOF”, “IMME”, “INNE”, “HOND”, “INOF” and “GOOE”. In other words, there are too many possible resultants to make users to effectively input words by traditional input methods and apparatus.
Therefore, what is needed is to provide a better encoding scheme and corresponding decoding method that can be easily realized by and accommodated to the users.